[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Carbonic anhydrase inhibitors

[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Carbonic anhydrase inhibitors

Weak diuretics that block carbonic anhydrase: they make the urine alkaline and lower eye pressure. Used in glaucoma and altitude sickness.

Updated 2026-11-01

## What they are

Sulfonamide inhibitors of carbonic anhydrase, the zinc enzyme that interconverts CO₂ and bicarbonate. Acetazolamide is the oral and IV member; dorzolamide and brinzolamide are eye drops for glaucoma.

## Mechanism of action

In the proximal tubule they stop bicarbonate reabsorption, so bicarbonate, sodium and water are lost in the urine and the blood becomes mildly acidic. In the ciliary body they reduce aqueous humour production, lowering eye pressure.

Target: Carbonic anhydrase (mainly CA II and CA IV)

## Key points

- Site: proximal convoluted tubule.
- Cause hyperchloraemic metabolic acidosis and alkaline urine.
- Uses: glaucoma, prevention of acute mountain sickness, some epilepsies, and as an adjunct in oedema.
- Adverse effects: paraesthesias, kidney stones, hypokalaemia, sulfonamide allergy.
- Contraindicated in cirrhosis: the alkaline urine keeps ammonia in the body and can trigger hepatic encephalopathy.

## Drugs in this class

- [**Acetazolamide** A carbonic anhydrase inhibitor that lowers eye pressure and causes a mild acidosis. Used in glaucoma and to prevent… Carbonic anhydrase II](https://durgical.com/en/pharmacology/acetazolamide/)

## Others in the class

- Dorzolamide
- Brinzolamide
- Methazolamide

## Test yourself

Think of the answer, then tap the question to see it.

## What acid-base disorder do carbonic anhydrase inhibitors cause?

Hyperchloraemic (normal anion gap) metabolic acidosis, from loss of bicarbonate in the urine.

## Why does acetazolamide help with acute mountain sickness?

The mild metabolic acidosis it causes stimulates breathing, which offsets the respiratory alkalosis of altitude and speeds acclimatisation.

## Why are carbonic anhydrase inhibitors avoided in cirrhosis?

Alkaline urine reduces ammonia excretion; the extra ammonia can trigger hepatic encephalopathy.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/classes/carbonic-anhydrase-inhibitors/)

[← All of pharmacology](https://durgical.com/en/pharmacology/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - ACETAZOLAMIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=240ab24b-3124-4805-80c2-36dd1945e3b3) (DailyMed (U.S. National Library of Medicine), 2026); [Acetazolamide: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682756.html) (MedlinePlus (U.S. National Library of Medicine), 2017); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=S01EC) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/pharmacology/classes/carbonic-anhydrase-inhibitors/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/carbonic-anhydrase-inhibitors/